The present invention relates to an apparatus for producing a lifting and lowering movement for lifting and lowering transverse transporting tongs of a forming machine. The apparatus according to the invention can be used both in hot-forming machines and in cold-forming machines.
In forming machines, the workpieces are often transported transversely by means of transverse transporting tongs from one forming station to the next and the empty transverse transporting tongs are then transferred back again into the starting position. From WO 98/14289 it is known, for example, to couple the transverse transporting tongs to a transverse transporting tube by means of a tong case and to displace the tong case, with the transverse transporting tongs holding the workpieces, from the starting position into the release position by means of displacing the transverse transporting tube in the longitudinal direction of the tube. As this happens, the tong case, provided with a roller, rolls on a rule fitted on the anvil. For guiding the empty transverse transporting tongs back after releasing the workpieces, the tong case with the transverse transporting tongs is lifted by turning the transverse transporting tube and is transferred back into the starting position by displacing the transverse transporting tube back in the longitudinal direction of the tube and lowering the tong case again. The raising of the transverse transporting tongs during the return transfer serves the purpose of avoiding the forming tools.
The lifting and lowering of the transverse transporting tongs takes place by the pivoting of a double lever, having a control roller arm and a counter roller arm, by means of a control cam and a counter cam, which are fitted on a rotatable control shaft and act on the double lever in opposite directions of rotation. For this purpose, a control roller, rolling on the control cam, is rotatably arranged on the control roller arm and a counter roller, rolling on the counter cam, is rotatably arranged on the counter roller arm.
The fact that the transverse transporting tongs are not lifted during the displacement from the starting position into the release position and the tong case rolls on the rule has the disadvantage that, if the rule or the tong case roller is soiled, an irregular movement takes place and the tong case is possibly inaccurately placed in the release position and/or starting position. Furthermore, when the tong case is set down on the rule there may be vibrations or stresses, possibly causing deformations, due to an overdetermination on account of inaccuracies or soiling of the control cam, the counter cam, the double lever, the tong case etc. A further disadvantage is that the tong case is set down relatively hard when it is returned into the starting position.
In the case of the forming machines described in GB-B-730 321, the transverse transporting tongs are lifted and lowered again both during the transfer from the starting position into the release position and during the transfer from the release position into the starting position, in order to permit a turning of the transverse transporting tongs during the transverse displacement. The lifting and lowering takes place by pivoting a double lever, having a control roller arm and a counter roller arm, by means of a control cam and a counter cam, which act on the double lever in opposite directions of rotation. The control cam and the counter cam do not rotate here, but move back and forth. A control roller, rolling on the control cam, is rotatably arranged on the control roller arm and a counter roller, rolling on the counter cam, is rotatably arranged on the counter roller arm. A fixedly mounted spring presses the control roller arm with the control roller permanently against the control cam.
Although the lifting of the transverse transporting tongs both during the transfer from the starting position into the release position and during the transfer from the release position into the starting position does avoid the problems possibly occurring if the tong case rolls on the anvil or the rule, the further disadvantages mentioned above with respect to the transverse transporting and lifting apparatus known from WO 98/14289 still remain.
In view of the disadvantages of the previously known transverse transporting and lifting apparatuses described above, the invention is based on the following object. An apparatus for producing a lifting Land lowering movement for the lifting and lowering of transverse transporting tongs of the type mentioned at the beginning, with which the transverse transporting tongs can be lifted and lowered again in the desired way, is to be provided, it being intended in particular that a gentle lowering into the fully lowered position is possible and that an overdetermination over wide ranges as well as vibrations can be avoided.
The apparatus according to the invention for producing a lifting and lowering movement for lifting and lowering transverse transporting tongs of a forming machine is essentially constructed as follows: a control cam and a counter cam are fitted on a movable cam carrier. A pivotably mounted double lever has a control roller arm and a counter roller arm, with a control roller, rolling on the control cam, being rotatably arranged on the control roller arm and a counter roller, rolling on the counter cam, being rotatably arranged on the counter roller arm, and the control cam and the counter cam acting on the double lever in opposite directions of rotation. The apparatus also comprises a movable spring element cam, on which there rolls a spring element roller arranged on a spring element lever, and a spring element, which is arranged on the spring element lever and acts on the double lever in the same direction of rotation as the counter roller.
The fact that, in addition to the control cam, the counter cam and the double lever, a spring element cam and a spring element lever with a spring element are present means that the lifting and lowering movement can be controlled alternately by the control cam and the counter cam on the one hand and by the control cam and the spring element cam on the other hand. Control by the control cam and the spring element cam is appropriate in particular in the region of the fully lowered position of the transverse transporting tongs, in order on the one hand to ensure a setting down with virtually no velocity, i.e. gentle setting down, of for example a tong case carrying the transverse transporting tongs on the anvil or a plate and on the other hand to prestress the transverse transporting tongs downward, so that neither vibrations nor overdetermination takes place, as would be the case if the control cam and the counter cam were to act on the double lever at the same time as the anvil or the plate act on the tong case. Controlling by the control cam and the counter cam is appropriate on the other hand in the middle and higher lifting regions for the safe and precise guidance of the relatively heavy tong case with the transverse transporting tongs.
The spring element cam is advantageously fitted on the movable cam carrier and the double lever and the spring element lever are advantageously fitted rotatably on a common spindle. The apparatus can in this way be of a relatively simple construction and the spring element does not have to make way any more than necessary.
In a preferred design variant, the spring element cam and the counter cam have the same curved shape and are formed as a single cam. This makes the apparatus even more simple and inexpensive to produce.
In another preferred design variant, the spring element cam is formed separately from the counter cam. This makes it possible for the spring force to be varied suitably by corresponding shaping of the spring element cam.
The control cam, the counter cam and the spring element cam are preferably shaped in such a way that, in the fully lowered position of the transverse transporting tongs, the spring element roller bears against the spring element cam and the spring element exerts on the double lever a torque pressing the transverse transporting tongs downward, while the control roller is lifted off the control cam and the counter roller is lifted off the counter cam. As a result, in the fully lowered position only the spring element cam and the anvil are acting, via the resting tong case, in a way which provides prestressing and entirely eliminates any overdetermination.